發(fā)布時間：2019-05-23 19:34

【摘要】：本文采用TIG-MIG復(fù)合焊對AZ31鎂合金型材進行了焊接研究,主要研究了焊縫成形、微觀組織、力學(xué)性能。首先,進行了 TIG-MIG復(fù)合焊系統(tǒng)搭建,主要包括兩個部分:兩焊槍的夾持裝置設(shè)計和控制系統(tǒng)設(shè)計。其次是兩焊槍的相對位置關(guān)系的確定。適合本次試驗的兩焊槍的位置關(guān)系是:兩焊槍在同一直線上,TIG焊槍在前,MIG焊槍在后,TIG焊槍垂直與工件,MIG焊槍與TIG焊槍成45°夾角。然后研究了工藝參數(shù)(TIG焊電流、MIG焊電流、MIG焊電壓、焊接速度、TIG焊電弧與MIG焊電弧的中心距離)對焊縫成形的影響規(guī)律,最終獲得成形良好的接頭。對成形良好的焊接接頭進行了拉伸試驗,得出抗拉強度達到215MPa,約為母材的79.63%,接頭的斷裂形貌主要呈現(xiàn)為韌窩斷裂與解理斷裂的混合型斷裂。對焊接接頭進行了硬度試驗,得出焊縫硬度的平均值為57.78HV、熱影響區(qū)硬度的平均值為52.81HV、母材硬度的平均值為56.14HV。對焊接接頭進行了微觀組織研究,研究結(jié)果表明焊接接頭由母材區(qū)、熱影響區(qū)、焊縫區(qū)組成。母材的微觀組織為較均勻,晶粒細(xì)小,主要由α-Mg相組成。熱影響區(qū)的微觀組織呈現(xiàn)晶粒粗大而又不規(guī)則,有少量的β-Mg17Al12金屬間化合物。焊縫為細(xì)小均勻的等軸晶,主要由α-Mg相和β-Mg17Al12金屬間化合物兩個部分組成。β-Mg17Al12金屬間化合物主要分布在晶粒和晶界上,呈現(xiàn)條狀和粒狀。最后對比分析了 TIG-MIG復(fù)合焊高速焊與低速焊的接頭宏觀、微觀、硬度。從宏觀上比較,高速焊接的焊縫表面魚鱗紋更細(xì)和熔寬更寬。從微觀上比較,高速焊接的熱影響區(qū)與焊縫晶粒比低速焊接的相應(yīng)區(qū)域更細(xì)小。從接頭硬度比較,高速焊接的熱影響區(qū)硬度和焊縫硬度比低速焊接的相應(yīng)區(qū)域大。
[Abstract]:In this paper, TIG-MIG composite welding was used to study the welding of AZ31 magnesium alloy profiles. The weld forming, microstructure and mechanical properties were mainly studied. Firstly, the TIG-MIG composite welding system is built, which mainly includes two parts: the clamping device design and the control system design of the two welding guns. Secondly, the relative position relationship of the two welding guns is determined. The position relationship between the two welding guns is as follows: the two welding guns are in the same straight line, the TIG welding torch is in front of the MIG welding torch, the TIG welding torch is perpendicular to the workpiece, and the MIG welding torch is 45 擄angle with the TIG welding torch. Then the influence of process parameters (TIG welding current, MIG welding voltage, welding speed, center distance between TIG welding arc and MIG welding arc) on weld forming is studied, and finally the well formed joint is obtained. The tensile test of the well-formed welded joint shows that the tensile strength is 215 MPA, which is about 79.63% of that of the base metal, and the fracture morphology of the joint is mainly the mixed fracture of dimple fracture and cleavage fracture. The average hardness of the welded joint is 57.78 HV. the average hardness of the heat affected zone is 52.81 HV. the average hardness of the base metal is 56.14 HV. the average hardness of the welded joint is 57.78 HV. the average hardness of the heat affected zone is 52.81 HV. the average hardness of the base metal is 56.14 HV. The microstructure of the welded joint is studied. The results show that the welded joint is composed of base metal zone, heat affected zone and weld zone. The microstructure of the base metal is uniform and the grain size is fine, which is mainly composed of 偽-Mg phase. The microstructure of the heat affected zone is coarse and irregular, and there are a small amount of 尾-Mg17Al12 intermetallic compounds. The weld is a fine and uniform equiaxed crystal, which is mainly composed of 偽-Mg phase and 尾-Mg17Al12 intermetallic compound. 尾-Mg17Al12 intermetallic compound is mainly distributed on grain and grain boundary, showing strip and grain shape. Finally, the macro, micro and hardness of high speed welding and low speed welding of TIG-MIG composite welding are compared and analyzed. From a macro point of view, the fish scale lines on the weld surface of high speed welding are thinner and wider. Compared with the corresponding area of low speed welding, the heat affected zone and grain size of high speed welding are smaller than those of low speed welding. Compared with the hardness of the joint, the hardness of the heat affected zone and the hardness of the weld in the high speed welding are larger than those in the low speed welding.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG456

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本文編號：2484167